I get fairly consistently 21 in town and I'm not light on the accelerator either. I've found that at freeway speeds I get better mileage at 80mph than say 70 or 72. I get 27 to 28 mpg at 80 and about 24 to 25 at 70-72. I have driven a number of times back home from Portland and also made some jaunts to Seattle and it always does this consistently. I have 20" tires too. My two cents.

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2007 328i Sport, Monaco Blue
2011 X35D - sold -Space Grey
2004 X5 4.4i - sold - Kalahari Beige
2001 X5 3.0i - sold - Pearl Beige
2006 325i Sport, Sonora Beige
2000 323i - sold - Sienna Red